The present invention relates to an interactive distribution system for audio-video signals, having a channel called downstream channel and a channel called upstream channel, the downstream channel transmitting signals in the form of digital packets from a server to users, a clock intended for multiplexing upstream messages from the users to the server being defined by markers whose position is periodically indicated by a number, called pointer, incorporated in one of the packets of the downstream channel, this pointer indicating the time that is left between the moment where the pointer appears and the moment where the marker is placed.
The invention also relates to an audio-video signal for a system having a channel called downstream channel and a channel called upstream channel, which signal is transmitted in the downstream channel in the form of packets and comprises, inter alia, a clock, used for the multiplexing of messages in the upstream channel, defined by markers whose position is periodically indicated by a pointer incorporated in one of the packets, the value of this pointer indicating the time that is left between the moment where the pointer appears and the moment where the marker is placed.
The invention also relates to a method of calculating in an interactive digital audio-video signal distribution system that transmits signals from a server to users in the form of packets, the value of a pointer indicating the position of a time marker incorporated in one of the packets, the value of this pointer indicating the time that is left between the moment where the packet containing the pointer appears and the moment where the marker is placed.
The invention is applied to interactive digital systems operating in networks such as cable and satellite networks.
An interactive distribution system for digital audio-video signals as defined in the opening paragraph is specified by the standards ETS 300 800 and DAVIC (ETS-European Telecommunication Standard). This standard provides a clock used for multiplexing upstream messages from the users to the server, which is defined by markers whose position is periodically indicated by a number, called pointer, incorporated in a packet.